Exporting a real 20 MP CR2 failed every time with "readback did not
complete", while the copy itself was perfectly healthy.
The bound was 100,000 non-blocking polls. That sounds generous and is not: a
`Poll` that finds nothing returns immediately, so the loop spent its entire
budget in a few milliseconds. Small transfers — the histogram's 4 KB, a
viewport-sized frame — happened to land inside it. An 80 MB frame never could.
It is a deadline now, thirty seconds, which is the only thing the bound was
ever for: catching a lost device that will never deliver the callback. A
one-millisecond pause after the first sixty-four spins stops the loop
saturating a core for the length of the copy, while keeping a small transfer
as immediate as it was.
Found by developing /home/dtourolle/Downloads/_MG_8596.CR2 through the export
example: 5472×3648 renders in 127 ms and writes all five formats.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
dtourolleandClaude Opus 5
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